Cyclic machine control system



Oct. 10, 1961 v. H. slMsoN CYCLIC MACHINE CONTROL SYSTEM Filed July 2,1957 'www M. 5D'

NA A United States Patent Office 3,004,202 n Patented oct. 1o, 19613,004,202 ,l CYCLIC MACHINE CONTROL SYSTEM Verne H. Simson, Milwaukee,Wis., assguoi' to Cutler- Hammer, Inc., Milwaukee, Wis., a corporationof Delawarer Filed July 2, 1957, Ser. No. 669,596 13 Claims. (Cl.S18-216) This invention relates to cyclic machine control systems andsafety apparatus therefor.

While not limited thereto, the invention is especially applicable toalternating current motor direct drive punch presses and the likewherein failure of the control system to stop the motor or to functionin a predetermined manner might result Iin serious injury to personnelor damage to the machine. n

Gn this type of press, the main drive motor is started and stopped witheach operating cycle of the ram. This subjects the contactors whichconnect the motor directly across the line as Well as the motor to verysevere service. For purposes of safety, heretofore known systems haveemployed two-pole reversing contactors with a threepole main contactorahead of the latter for connecting the power supply source to the motor.Use of the aforementioned arrnngementof contactors entails aconsiderable amount of interlocking requiring a large number ofelectrical interlocks in the control 'circuits of the contactors therebyintroducing weak characteristics to electromagnetic switches which areotherwise long life devices. It is therefore desirable to provide asimplified motor control system having improved means which not onlyeliminate Ithe aforementioned weak characteristics while retaining theinterlocking functions but yalso afford protection lagainst failure ofanyone of a maximum number of control devices in such system.

Accordingly, a primary object of the invention is to provide meansaffording the aforementioned and other improved results.

A more specic object of the invention is to provide a machine controlsystem having improved electrical interlocking means.

Another object of the invention is to provide improved means atfordingmaximum protection against failure of control devices in such system.

Another specific object of the invention is to provide an improved andsimplied motor control system having incorporated therein meansaffording protection against failure of all operating elements of thesystem.

A further object of the invention is to provide improved means affordingpositive protection to personnel in the event of failure of motor powercircuit elements in such control system.

Further objects and advantages of the invention will hereinafter appear.

While the invention hereinafter described is effectively adapted tofulfill the objects stated, it is to be understood` that l do not intendto coniine my invention to the particular preferred yembodiment. ofmotor control system disclosed inasmuch as it is susceptible of variousmodifications without departing from the scope of the appended claims.

The single iigure of the drawing diagrammatically illustrates a motorcontrol system constructed in accordance with the present invention.

Referring to the drawing, there is shown `a three-phase induction motorM of the squirrel cage type or the like having a primary'winding P and asecondary winding S. A three-phase power supply source is connectible tothe primary winding P of motor M through the usual onofi switchestnotshown) to lines L1, 'L2 and L3 andy then through norm-ally open contactsCB2-4 of a circuit breaker CB, normally open contacts 1M2, 2M2 and SM2 2of main contactors 1M, 2M and 3M, respectively, normally open contacts1132 and 2PZ of forward contactors 1F and 2F and through operating coilsOLI, CL2 and CL3, respectively, of overload relay OL to primary windingP. Motor M is connected to drive press 2 through a shaft 4. Anelectromagnetic brake is interposed between the motor and the press andhas a brake drum 6 connected to shaft 4. Spring applied brake shoe 8 isoperated in the usual manner by the brake mechanism BR.

The control system shown in the lower portion of the drawing is providedwith a forward control relay FCR having an operating coil FCRI connectedacross lines L1 and L3 through normally closed contacts 11:3 and 2F3 ofthe respective forward contactors 1F and 2F. A control relay 3CR has anoperating coil 3CR1 connected across lines L1 `and L3 through a normallyclosed emergency Stop switch 10 and normally closed contacts 12 and 14of Run switches 16 and 18, respectively. Run switches 16 and 18 arepreferably mounted sufficiently spaced apart as `a safety measure tooccupy both hands of the operator and thus to prevent accidentallyplacing the latter in the machine while in operation. A pair of timingrelays ITR and 2TR have their operating coils lTRl and ZTRI,respectively, series connected in a circuit extending from line L1through a half-wave rectifier 20 to a common point 22 where the circuitdivides. One branch extends through normally closed contacts FCRS to acommon point 24 while another branch extends through normally closedcontacts 1MCR3 ofan interlocking relay IMC?. and normally closedcontacts 6CR3 of control relay 6CR to point 24, the latter beingconnected to line L3 on one hand through normally open contacts 6CR2 andin a parallel path on the other hand through normally closed contacts1MCR2 and 2MCR2 and normally open contacts FCRZ. Resistor R1 andcapacitor C are series connected in shuntof the operating coils 1TR1 andZTRI of the timing relays. Timing relays lTR and ZTR are provided withthis capacitor-resistor shunt circuit to afford timedopening of contactsITRZ and ZTRZ in the energizing circuit of a circuit breaker CB. nCircuit breaker CB has an undervoltage coil CB1 connected across linesL1 and L3 through normally closed contacts OL4 of overload relay OL,normally open contacts 1TR2 of timing relay lTR and normally opencontacts 2TR2 of timing relay ZTR.

A non-repeat relay N is provided having an operating coil N1 connectedacross lines L1 and L3 through Stop switch 10, conductor 26, normallyclosed limit switches 1LS1 and 1LS2 and normally open contacts 3CR3 ofthe aforementioned control relay SCR. Relay N is provided with normallykopen contacts N2 for establishing a holding circuit for itself inshuntof contacts SCRS when the relay is energized. A control relay iCR isprovided having an operating coil 1CR1 connected across lines L1 and L3through Stop switch 10, normally open contacts 28 of Run switch 16,normally open contacts 30 of Run switch 18, normally open contacts N3 ofrelay N, normally closed contacts 3CR2 ofl relay 3CR, normally closedcontacts 1MCR5 and 2MCR4 of interlocking relays IMCR and ZMCR,respectively, and normally open contacts FCR5. Control relay ICR ispro-k vided with normally open contacts 1CR2 for establishing a holdingcircuit for itself in shunt of contacts lMCRS, 2MCR4 and FCRS. A controlrelay ZCR is provided having an operating coil ZCRI, series connectedwith normally open contacts 1CR3 of control relay lCRin shunt of theoperating coil of the latter for energization in response to energizingof the operating coil of relay lCR and closure of its contacts 1CR3.

A full-wave rectifier bridge DR is connected at its input terminalsacross lines L1 and L3 through normally open contacts ICR4 of controlrelay ICR, conductor 32, con.-

tacts FCRS, ZMCRd, IMCRS, 3CR2, N3, 36 and 28 and Stop switch It). Theaforementioned holding circuit for relay ICR throughits contacts ICRZalso-.acts to maintain energization of the operating coil ZCRI of relayZCR and rectifier bridge DR Yas will hereinafter appear. A `furthercircuit for maintaining energization `of rectifier bridge DR is providedthrough contacts ICR4, normally open contacts ZCRfi of control 'relayZCR, normallyopen limit switches ZLSI' and ZLSZ, conductor'26 and Stopswitch It), the latterv circuit through switch iti, limit switches ZLSIand ZLSZ and contacts ZCRi also providing a holding circuit for theoperating coils of relays ICR and ZCR as will be apparent.

Operating coils IMI, ZMI and SMil .of the respective main contactors areseries connected with a resistor R2 across the positive and negativeoutput terminals of rectifier bridge DR. Operating coil oCRI of theaforementioned control relay 6CR is also connected across the positiveand negative output terminals of rectler bridge DR. Similarly, operatingcoils 1F I and ZFI of the aforementioned forward contactors IF and 2Fare series connected with normally open contacts 2CR2, IMCR4 and ZMCRSand resistor R2 across the output terminals of bridge DR. Theaforementioned circuit may be traced from the right-hand positiveterminal of rectier bridge DR through conductor 34 to common point 36where it divides. One branch extends through operating coil GCRI andconductor 3S to the negative terminal of bridge DR; another branchextends through resistor R2, operating coils IMI, ZMI and SMI andconductor 38 to the negative terminal of bridge DR; while a third branchextends through resistor RZ, contacts ZMCRS, 1MCR4 and 2CR2 andoperating coils IFI and EFI to the negative terminal of bridge DR.Normally open contacts FCR-4i of relay FCR are connected to shuntresistor R2 effectively out of the circuit for reasons more fullydescribed hereinafter. The aforementioned interlocking relays IMCR andZMCR have their operating coils connected across lines Lil-L2 and LI-LS,respectively, between the contacts of the main and forward contactors.Although reversing contactors in addition are employed in actualpractice, they have been omitted herein as unnecessary for descriptionand'understanding of the presentV in- Ventron.

Press 2 is of the direct drive type.r The press operates when motor Moperates and is stopped when the motor is stopped. rEhe control circuitis arranged for non-repeat operation of the press. That is, the pressoperator must operate the Run switches to initiate each cycleofoperation of the press and he must release the Run switches beforeanother cycle of press operation canbe initiated contactors IM, 2M and3M, motor forward contactors,

1F and 2F and control relay 6CR; these contactors and relay beingenergized by unidirectional output current from rectifier bridge DR. Y

The ilow of alternating current input power to rectier bridge DR and theenergization of brake BR are controlled by the second or non-repeatportion of the control circuit. This portion comprises relays ICR, ZCR,BCR and N, Run switches 16 and I8, stopY switch Iii and limit switchesILSI, ILSZ, ZLSI and ZLSZ.

The third portion of the control circuit functions to insure that themotor is stopped in the event that some part or component of the controlcircuit should malfunction. This portion comprises undervoltage circuitbreaker CB, forward control contactor FCR, main control or interlockingrelays IMCR and ZMCR, timing relays ITR and ZTR, half-wave rectifier 20,capacitor C, resistor RI and overload relay OL.

The limit switches shown in the lower left-hand portion of the drawingare connected to the press 2 and motor My directly or indirectly and aremechanically or electri cally operated in accordance with the movementof the press ram. Diagram 40 depicts the operating characteristics ofthe limit switches shown at the right-hand end thereof for one fullcycle of the press. The vshaded areas depict the closedconditions'of the`corresponding limit switches whereas the unshaded areas depict the`open conditions thereof. Diagram 40 is a layout development of a cam orthe .like .type'ofzlimit switch actuator operable from zero degrees to`'560.de'grees in the direction of the arrow during each complete cycleof and conjointly with the press'. The right and left-hand ends ofdiagram 4G, marked zero and 360 degrees, respectively, indicate theuppermost position of the press ram. The central degree point indicatesthe lovvermost position of the ram.

The reversing circuit, inching circuit and various signal light andother auxiliary circuits have been omitted from the drawing to avoidcomplicating the latter and because they do not change the essentialcharacter of the invention.

Let it be assumed that the aforementioned on-off switches are closed ltosupply three-phase alternating current power to lines LI-S. A circuitis'comple'ted for energizing operating coil FCRI of relay FCR from lineL3 through contacts IFS and 21:3 to line L1. A circuit is also completedfrom line L3 through Stop switch It), contacts I2 and I4 of the Runswitches and operating coil SCRI to line LI for energizing control relaySCR'. Relay FCR energizes vand closes contacts F-CRZ to'energizeoperating coils ITRI and'ZTRI of the timing relays in a circuitextending from line L3 through contacts FCRQ, ZMCRZ f and IMCR2, point24, contacts 6CR3` and ILMCRS, point 22 and rectifier 20 to line L1.Timed opening contacts ITRZ and ZTRZ close and energize the undervoltagecoil CB1 of'circuit breaker CB in a circuit extending from line L3through contacts CL4, 1TR2 and* ZTRZ to line LI. Circuit breaker' CB'closes contacts CB2-4 to prepare an energizing circuit to themotor-primary winding P to be completed as hereinafterdescribed.l

The aforementioned energization of relay FCR also opens contacts FCRS inshunt of 'normally closed contacts 6CR3 and' IMCRS in the timing relaycircuit to provide a safety feature hereinafter described. Furthermore,contacts FCR4 close to shunt resistorRZ effectively out of circuit withthe main and forward power contactors to provide a higher voltage Vforrapid energization of the latter as hereinafter described. Contacts FCRSclose a point in the energizingcircuit ofcontrol relay ICR.

Upon energization of relay 3CR as. heretofore described, contacts SCRZopen to prevent operation of control relay ICR until the Run switchesare pressed, and

contacts SCRS close to complete an energizing circuit forv operatingcoil N1 of relay N. This circuit may be traced from line L3 throughswitch I0, conductor 26, limit switches ILSIand ILSZ, and contacts 3CR3to line LI. Relay N closes contacts N2 to complete a holding circuit inshunt of contacts SCRS. Contacts N3 close a further point in theenergizing circuit of control relay ICR.Y

The control system is now in a preparatory condition wherein` operationof the press can be initiated byvpressing Run switches I6'and`18.vPressing Run switch I6 results in opening of contacts I2 and closure ofcontacts 2S while pressing Run switchA 18 opens contacts I4 and closescontacts 30. Opening of contacts I2 and I4 interrupts the energizingcircuit of operatingcoil 3CR1 .to release relay SCR. Contacts SCRS openwith no effect because reiay N is 'maintained energized at contacts NZ.Closure of contacts SCRZ completes a further point in the energizingcircuit of relay ICR. Upon' the closure of contacts 28 and 30 of theRunV switches, operating coil I-CRI is energized in a circuit extendingfrom line L3, switch Iii and contacts 28, 30, N3, 3CR2, IMCRS, ZMCRQ!and FCRS to line LI. Contacts ICRZ close to xcomplete ya holding circuitin shunt of contacts FCRS, 2MCR4 and IMCRS, and contacts 1CR3 close yto'cornplete an energizing circuit for operating coil 2CR1 of controlrelay ZCR in parallel ywith the operating coil of relay 1CR. Closure ofcontacts 1CR4 results in energization of rectifier bridge DR in acircuit extending from' line L3 through the aforetraced circuit tooperating coils 1CR1 and ZCRl and then through conductor 32, con-r tacts1CR4 and the input terminals of rectifier bridge DR to line L1. yControlrelay Z'CR being energized closes contacts 2CR2 to complete a point inthe energizing cir cuit of the forward contactors, and closes contacts2CR4` to close a point in a maintaining circuit for rectiiier bridge DRto be subsequently completed. Relay ZCR also closes contacts ZCRS toenergize brake winding BRI across lines L1-3 to disengage brake shoe 8from drum 6.

ln the meantime power is supplied to the primary winding P of motor M tostart the motor inthe following manner. Upon the aforementionedenergization of rectifier bridge DR, relay 6CR and main contactors 1M,2M and 3M are energized in parallel in a circuit extending from thepositive output terminal of bridge DR, conductor 34 to point 36 where itdivides. One branch extends through coil 6CR1 to conductor 38 whileanother branchv extends through contacts FCR4, coils 1M1, 2M1 and SM1and conductor 3S to the negative output terminal of bridge DR. Relay SCRcloses contacts 6CR2 to complete a holding circuit for the timing relaysin shunt of con-v tacts FORZ, ZMCRZ and IMCRZ, and opens contacts 6CR3.As will be apparent, opening of contacts 6CR3 interrupts the energizingand holding circuits of the timing relays. However, the timing relaysare provided with capacitor C and resistor Rl to render contacts 1TR2and ZTRZ slow-to-open, thus to prevent circuit breaker CB fromdisconnecting the motorin the short interval of ime before contacts PGR3reclose the timing relay energizing circuit, as hereinafter described.

. Upon being energized, the main contactors close their l respectivecontacts 1M2, 2M2 and SM2 to complete a further point in the powerconnections to the motor pri-1 mary winding P. Closure of the lastmentioned contacts completes energizing circuits therethrough, andthrough contacts CB2-4 of circuit breaker CB to operating coils QMCR.and lMCRll of interlocking relays ZMCR and lMCR, respectively. Relays1MCR'and ZMCR open contacts lMCRZ and ZMCRZ to further interrupt theenergizing circuit of the timing relays, and open contacts IMCRS andZMCPA with no effect as relay CR is maintained through contacts 16H2.Relay IMCR opens contacts 1MCR3 with no effect as contacts 6CR3 inseries therewith are already open. Furthermore, relays IMCR .and ZMCRclose contacts A1MCR4 and'ZMCRS to complete an energizing circuit foroperating coils 1F1 and 2F1 of forward contactors 1F and 2F. Thiscircuit extends from the positive output terminal of rectifier bridgerDR through conductor 34, point 36, contacts FCR4, ZMCRS, 1MCR4 and ZCRZand coils IFI and 2131 to the negative output terminal of bridge DR.Contactors 1F and ZFclose their contacts 1F2`and 2F2 to complete thepower connections for motor M to start the latter, and ,open contactsIFS and 2F3 to interrupt the circuit of forward control relay FCR anddeenergize operating coil FCRL Relay FCR closes contacts FCRS toreestablish a holding circuit for the timing relays before the latterhave timed out, extending from line L3 through contacts tiCRZ, point124, contacts PGR3, point 22 and rectifier 20 to line L1. Contacts FCRZand FCRS open without effect while contacts FCR4 open to reinsertresistor R2- r.effectively in the energizing circuit of the main andfor- 'y ward contactors.

The function of resistor R2 is to aifoird a voltage drop to decrease thevoltage on and protect operating coils 1li/l1, 2M1 and 3M1 of the maincontactors and operating coils 1F1 and 2F1of the forward contactors fromhigh voltage. Resistor R2 also decreases the current in sondeos the mainand forward contacter operating coilcircuits to afford rapiddeenergization of the latter at the end of the operating cycle of thepress as hereinafter described;

Motor M thus being energized operates press 2 through shaft 4. Let it beassumed that the limit switch actuator shown in the lower left-handportion of FIG. 1 operates from zero degrees to 360 degrees .conjointlywith one cycle of the press ram. When the ram reaches a position shortof its lowermost position, limit switches ZLSI and ZLSZ close asdepicted by the upper two and like shaded portions to the left of theseswitches. Closure of limit switches 2LS1 and 2LS2 completes theaforementioned circuit for maintaining rectier bridge DR energizedindependently of the Run switches in a circuit extending through Stopswitch 10, conductor 26 and contacts 2CR4 and 1CR4. The main and forwardcontactors and relayCR are also maintained energized across the outputterminals of the rectierbridge. Moreover, conductor 32, being connectedto the junction of contacts 2CR4 and 1CR4 applies the aforementionedmaintaining circuit to operating coil 1CR1 or relay ICR and throughcontacts 1CR3 of the latter to operating coil `2CR1 `of relay ZCR.

The Run switches 16 and 18 may now be released without stopping thepress. It should be observed, however, that the press can be stopped atany position of its cycle vby depressing Stop switch 10 as will beapparent.

Release ofthe Run switches results in opening of confk tacts 28 and `3Gwithout etfect and closure of contacts 12 and 14 to complete anenergizing circuit for operating coil 3CR1 of relay SCR. Contacts 3CR2open and contacts SCRS close without effect at this time. The press ramis suiiiciently near its lowermost position at this time to precludethedanger of the operator placing his hands thereunder. i f n When thepress ram reaches a further position depicted by the lower two and likeunshaded portions to the left* of limit switches lLSl and 1LS2, thelatter open to deenergize the operating coil of relay N, openingcontacts" N2 and N3. The latter contacts perform no useful function atthis time because the Run switches were heretofore released. and 1LS2when the ram reaches a position indicated by the two lower, left-handshaded portions to the left of these switches results in reenergizationof relay N and yclosing of contacts N2 and N3, contact N2 reestablishingthe aforementioned holding circuit in shunt of contacts 3CR3. When thepress ram approaches its uppermost position at the end of the cycle,limit switches 2LS1 and ZLSZ open to stop the press. Opening of limitswitches 2LS1 and ZLSZ interrupts the circuit through Stop switch? 1t),conductor 26 and contacts 2CR4 and 1CR4 whereby rectiiier bridge'DR andrelays lCR and ZCR were maintained energized. Relays ICR and ZCRdeenergize. Main contactors 1M, 2M and 3M, forward contactors 1F and 2Fand controlfrelay 6CR which were fed through bridge DR deenergize. Themain and forward contactors interrupt the motor power connections whilecontrol relay ZCR opens contacts ZCRS to deenergize brake wind-` ing BRIwhereupon brake shoe 8 is spring applied to stop the motor and press.Forward contactors 1F and 2F reestablish the energizing circuit of relayFCR through contacts 1F3` and ZFIS while interruption of they motorpower connections by the main contactors also interrupts the energizingcircuits for relays IMCR and 2MCR to deenergize the latter. This returnsthe control system to the aforementioned preparatory condition, whereinre-k lays FCR, 3CR, 1T R, ZTR and N and circuit breaker CB are energizedwhile the remaining contactors and relays are deenergized. Thus it isseen that for each time that Run switches 16 and 18 are pressed, thepress operates through one complete cycle and automatically stops atnthe end thereof.

Limit switches 1LS1 and 1LS2 providefthe non-repeat function wherein thepress automatically stops at the end of each cycle even in the event theRun switches are noty Subsequent closure of limit switches 1LS1Y'sportarts released. Should the Run switches be held depressed, limitswitches lLSl and 1LS2 open as before when the press ram approaches itslowermost position to deenergize relay N. Contacts N2, interrupt itsholding circuit while contacts N3 interrupt the initial energizingcircuit of control relays lCR and ZCR and rectifier bridge DR. Now whenlimit switches lLSl and lLSZ reclose near the end f the cycle, relay Ndoes not reenergize because the Run switches are depressed, relay 3GB'is deenergized and contacts 3CR3 in the circuit of relay N are open. Asthe press ram is driven further, limit switches ZLSll and ZLSZ open torelease the system, interrupt the motor power connections and apply thebrake as heretofore described. Thus, it will be apparent that automaticstopping is afforded at the end o-f each cycle of the press ram when theRun switches are pressed and released in the normal manner and 'also inthe event the Run switches are pressed and held depressed throughout thecycle. It will also be apparent that in the latter case the press cannotbe restarted unless the Run switches are released to energize relay Nfollowing energization of relay SCR and then pressed again to initiateanother cycle of operation.

lOperating on the hop describes a repeat operation, that is, operatingthe press through a plurality of successive cycles without interruption,obtained by timed manip ulation of the Run switches by an experiencedoperator. This is obtained by releasing the Run switches after limitswitches 2LS1 and ZLSZ have closed and reoperating them during asubsequent interval of time. Relay CR energizes upon release of the Runswitches and closes contacts 3CR3 to prepare an energizing circuit forrelay N. Near the end of the punch press cycle during `the interval oftime between the closure of limit switches lLSl and lLS-Z and theopening of limit switches ZLSl and 2152, the operator presses the Runswitches. Closure of limit switches lll/S1 and lLSZ reenergizes relay Nwhich closes contacts N2 to maintain its energization and closescontacts N3 to prepare the initial energizing circuit for relay ICR. Asthe Run switches are pressed, contacts l2 and 14 open to deenergizerelay SCR thereby to close a fun ther point in the aforementionedinitial energizing circuit at contacts 3CR2, and contacts 28 and 3Gclose to cornplete the initial energizing circuit for relay lCR. Thus,subsequent opening of limit switches ZLSl and ELSE near the end of thecycle does not result in interruption of thc system and motor operationis maintained for a repeat cycle. It will be noted that in order toobtain operation on the hop, the Run switches must be pressed during theaforementioned interval but after relay N has reencrgized.

The press can be stopped at any position of its operating cycle bymomentarily pressing emergency Stop switch l@ to release the controlsystem as heretofore described. The inching apparatus which would thenbe employed to operate the press ram to its uppermost position has beenomitted herein as unnecessary to the present invention.

An essential feature ofthe invention resides in the provision ofcircuits and arrangements affording utmost safety to the press as wellas to operating personnel.

Two manual Run switches are employed to occupy both hands of theoperator until the press ram approaches its lowermost position to anextent that there is no longer danger of the operator placing a handunder the ram. Two series connected limit switches are employed in eachcase so that failure of one thereof will not prevent automatic stoppingof the press. Moreover, two timing relays are provided to insure thatfailure of one to time` out will not prevent release of the circuitbreaker by the other.

The most dangerous thing from the safety standpoint is that the controldos not function to stop the press when required. In order to insurethat the press does stop under such conditions, two sets of contactors,main and forward, are employed in the motor power circuit. In addition,interlocking arrangements are provided in the timing relay circuit. Theelements which indicate that the motor power switches operate in therequired manner are arranged to be fail-safe, that is, any failure onthe part of these indicators will not prevent protection against suchfailure so as to cause the press to keep running. In this connection twoassumptions have been made: (l) that two failures will not occursimultaneously' and (2) that all parts of the relays operate together,that is, when normaily open contacts close, normally closed contactsopen and vice versa. For additional safety, assumption (2) has not beenextended 'to the main and forward contactors as protection is affordedagainst partial failure of thc latter.

As will hereinafter appear, the system is fail safe under all abnormalconditions, that is, under certain abnormal conditions the circuit willstop the motor while under other abnormal conditions the motor will notstart at all. Initially relays FCR, ECR, lTR, ZTR and N and circuitbreaker CB are energized preparatory to starting the motor, asheretofore described. Of course, if any one of these elements initiallyfails to operate, the motor will not start at all.

Let it be assumed Athat the system is in the aforemen; tionedpreparatory condition and that the Run switches are pressed to initiatestarting of the motor. ln the following description, the termm closewhen used in connection with an electromagnetic device will beunders-tood to have reference to closure of normally open contacts andopening of normally closed contacts of such electromagnetic device whilethe term open will be understood to mean the reverse of c1o se, that is,opening of normally open contacts and closure of normally closedcontacts of such device. Failure to close or open may be due tomalfunctioning of any part ,of such device.

When starting the press:

If relay dCR fails to close, the energizing circuit of operating coilslTR and 2TR of the timing relays will remain open at contacts 6CR2 andIMCRZ and ZMCRZ. After a predetermined time delay, the timing relayswill interrupt the energizing circuit of the undervoltage coil ofcircuit breaker CB to open the latter and stop the press.

if either main contacts ZMZ or aMZ fail to close, the motor will notstart; and the circuit breaker opens because contacts SCRS and FCRSremain open to open the timing relays.

lf main contacts lMZ fail to close, the motor will not start.

if either relay IMCR or ZMCR fails to close, the motor will not start;and the circuit breaker opens because conltacts 6CR3 and PGR3 remainopen as before.

If either contacts lF2 or 21:2 fail to close, the motor will not start.

If either contacts llFS or ZPS fail to open, the circuit breaker opensbecause contacts 6CR3 and FCR3 remain ouen.

If relay FCR fails to open, the circuit breaker opens because contacts6CR3 and FCRS remain open as before.

When stopping the press:

If relay GCR fails to open, the circuit breaker opens because contactsdCRS and FCRS remain open.

If either contacts lFZ or 2PZ fail to open, the main contactors stop thepress.

If either contacts lFS or 2F31 fail to close, the circuit breakerdisconnects the motor because contacts CRZ and FCRZ remain open.

If any of the main contacts lMZ, ZMZ or SM2 fail to open, the forwardcontactors will stop the motor.

If main contacts ZMZ or SM2 fail to open, the motor will stop; and thecircuit breaker opens because relays lMCR and ZMCR remain energized andcontacts GCRZ, ZMCRZ, lMCRZ, FCRS and lMCRS remain open in the timingrelay circuits.

lf relay lMCR fails to open, the circuit breaker disconnects the motorbecause contacts 1MCR2 and 6CR2 remain open.

enoteca.A

` lf relay ZMCR fails to open, the circuit breaker disconnects the motorbecause contacts 6CR2 and ZMCRZ remain open in the timing relay circuit.

lf relay FCR fails to reclose, thecircuit breaker disconnects thek motorbecause contacts 6CR2 and FCRZ remain open in the timing relay circuit.

Finally, if an overload, or unbalanced condition occurs in the motorpower circuit, contacts OL4 open the main circuit breaker.

rl`hus it should be apparent that the invention provides a fail-safecyclic machine control system that not only aords protection topersonnel by preventinga continuous running condition of the machineshould control devices malfunction but also protects the machine fromdamage by work pieces lodged therein. Moreover, the invention providesfor opening of the main circuit breaker in the event of failure of oneof the motor power contactors, as for example, welding of the contacts,to aiord positive protection to personnel not heretofore obtained.

I claim: l y

l. ln a cyclic machine control system having vfirst and secondelectroresponsive switches which must be closed to connect powertherethrough to energize the machine and means responsive to initiationof operation of the machine for closing said irst switch, incombination, means responsive to closure of said first switch forclosing said second switch to eiect one cycle of operation of themachine, means responsive to termination of said one cycle forautomatically opening said switches, and means responsive to afailure ofeither the second or third mentioned means to operate properly forstopping the machine.

2. In a control system for an electrical motor driven machine whichsystem comprises electroresponsive control devices initially operablepreparatory to manually initiating operation of the machine, and manualmeans for initiating such operation, the combination withelectroresponsive means responsive to said manual means for connectingpower to the motor for operating the latter,

` follower means responsive to a predetermined driven movement of themachine for initiating stopping of the` latter, means comprising saidelectroresponsive means and responsive to said follower means fordisconnecting power from the motor to eiect stopping of the latter and amain power circuit breaker, of means responsive to failure of anyportion of said electroresponsive means to function in a predeterminedmanner for operating said circuit breaker.

3. The combination according to claim 2, wherein the last mentionedmeans comprises timing means for operating said circuit breaker apredetermined time interval after occurrence ofsuch failure, said timeinterval being longer than the difference in the normal operating timesof said electroresponsive means to prevent inadvertent operation of saidcircuit breaker.`

4. In a cyclic control system for an electrical motor driven machinewhich system comprises vfirst and second electroresponsive switcheswhich must be closed to effect operation of the machine and meansresponsive to initiation of operation of the machine for closing saidfirst switch, in combination, interlocking means responsive to' closureof said first switch for closing said second switch to eiiect operationof the machine, an electroresponsive circuit breaker normally connectingpower to said first switch and therethrough and through said secondswitchA when closed to the motor, and means responsive to a. failure ofsaid first and second switches or said interlock ing means to operateproperly for operating said circuit breaker to deenergize the motorpower connections.

5. The combination according to claim 4, wherein the last mentionedmeans comprises electroresponsive timing: means having an energizingcircuit and said interlocking means comprises at least koneelectroresponsive device energzable through said first switch and havingcontacts `for controlling said energizing circuit.

6. The combination according to claim 5, wherein said,

timing means comprises a pair of series connected timing relays eachhaving timed operating contacts for control-i ling said circuit breakerso that if one of said relays failsL the other relay will function toprevent operation of the machine.

7. In a control system for an electrical motor driven machine, thecombination with a rmotor power controll circuit and an operatingcontrol circuit, of a fail-safe con-' trol circuit, the last mentionedcontrol circuit having means incorporated therein to insure that themachine is: stopped in the event that a portion of the control system?malfunctions, said means comprising a main circuitA breaker forconnecting power to the main power control circuit, timing means forcontrolling said main circuitbreaker, and control means responsive tomalfunctioning breaker to disconnect power from the motor power con trolcircuit.

9. In a control system for an electrical motor driven. machine, thecombination with a motor power control. circuit and an operating controlcircuit, of a fail-safel control circuit, the last mentioned controlcircuit havingA means incorporated therein to insure that the machineis.` stopped in the event that a portion of the control system.;malfunctions, said` means comprising a main circuit;

breaker for connecting power to the main power control; circuit, timingmeans for controlling said main circuit: breaker, control meansresponsive to malfunctioning off the motor power control circuit foractivating said timing; means to operate said circuit breaker thereby todiscon nect power from the motor power control circuit, andi meansincorporated in saidcontrol means responsive toi mulfunctioning of thelatter for activating said timing means to operate said circuit breakerthereby to discon neet power from the machine.

l0. In a control system for an electrical motor driven machine, thecombination with a main motor power con trol circuit having first andsecond electro responsive switches both of which must be operated toconnect power therethrough to energize the machine and an operatingcontrol circuit for closing said switches, of a failsafe controlcircuit, the last mentioned control circuit comprising meansincorporated therein to insure that the machine is stopped in the eventthat a portion of the control system malfunctions, said means comprisinga main circuit breaker for connecting power when closed to the mainpower control circuit, timing means having an energizing circuit forcontrolling said main circuit breaker, and control means responsive tomalfunctioning of the control system for interruping said energizingcircuit whereby to activate said timing means to open said circuitbreaker.

1l. The combination according to claim l0, wherein sad'last mentionedcontrol circuit comprises electro- 'responsive means for initiallycompleting said energizing power concitciiit te. prevent. opening said,circuit breaker duringl seid' intervalB l2 The combination with a,control. system ,for power driven machines which control systemcomprises a power Supply, SQiirce and. at least two serially connected.electra* IeSPQHei/e Switches each Qt which. must be closed te connectpower therethrough from said source to energize themachine and controlmeans .for initiating Starting and Stepping 0fA the machine, of controlmeans` for detecting afaulty condition of either ,one of `said switches,s aidcontrolrneans comprising electroresponsive means responsivetoiilitiaticn of, Starting ci the inachine during existence of suchfaulty condition for preventing energization of the. machine andresponsive to initiation 0f Stepping ,of the machine during existenceVof such f autly condition for deenergizing the machine.

1,3. The combinationwith a control, system for power driven machineswhich control system comprisesV a power` supply source and atleast twoserially connected electroresponsive switches each ofv which must herclosed. to

cenaezei'power-therethrough te energize the-.machineand control meansfor-operating said switches to initiate start-V in g and, stoppingvotthemachine, of means for detecting afalure; .o f o nef ofY said.switches to operate properly, said control means comprisingelectroresponsive means respon sive toinitiation ofstartingot themachine during existenceY ofsuchiailure for. disconnecting said powersupply source from said switches to prevent energization of then'iachinev andreseponsive-to initiation of stopping of the machineduring existence of suchifailure for disconnectingv Said power., supplysource fromsaid switches to deenereize-ihe-inachine,

Referancesiiteiiin the tile of this patent UNITED STATES PATENTS23444'16 Elliotet al. June 29, 1943` 2,736,009 Barniekel -.Feb. 21, 1956 2,753,493 Saives July 3, 1956 2,736,989: Smith-5...-- Mar. 26,1957

